System for the production of pressed board

ABSTRACT

A system for the production of pressed board (e.g., hardboard, fiberboard, particle board) comprises a plurality of conveyorbelt systems including at least one system for carrying mats of a compressible material through a continuously operating press and at least one belt system for the pressing of the mats apart from the transport operation. The two systems are formed with respective drive motors and means is provided for synchronously connecting or mutually controlling the two systems at least intermittently.

United States Patent Andresen et al. June 3 1975 SYSTEM FOR THE PRODUCTION OF 2,883,033 4/1959 Armstrong et a] 2l4/16.6 x PRESSED BOARD 3,173,976 3/1965 Paerels et a1. 425/455 X 3,428,505 2/1969 Siempelkamp 425/455 X 1 Inventors: g Andresen, Nleder-Ramstadt; 3,565,725 2/1971 Siempelkamp 425/455 x Wolfgang Reiners, Kapellen, Kr, 3,611,482 10/1971 Hutz 425/DlG. 200 Moers; Alfons Klassen, Krefeld, all of Germany Primary ExaminerRobert L. Spicer, Jr. [73] Asslgnee' S'empelkamp & Krefeld Attorney, Agent, or FirmKarl F. Ross; Herbert ermany Dubno [22] Filed: June 29, 1973 [21] Appl. N0.: 374,982

[57} ABSTRACT 30 FeinAl't' P"tDta 1 J 2; F pp ma on "on y a A system for the production of pressed board (e.g., 9 I972 germany hardboard, fiberboard, particle board) comprises a many 31 plurality of conveyor-belt systems including at least I one system for carrying mats of a compressible mate- [52] '2f rial through a continuously operating press and at 4257010 least one belt system for the pressing of the mats apart [51] I t Cl B29d'7/14 from the transport operation. The two systems are [58] 1 5' 5 371 335 formed with respective drive motors and means is prog i dd /151 4 vided for synchronously connecting or mutually controlling the two systems at least intermittently.

[56] References Cited UNITED STATES PATENTS 12 Claims, 5 Drawing Figures 1,903,102 3/1933 Farley 2l4/l6.6 X

PATENTED 3 1975 wN QN PATENTED N SHEET SYSTEM FOR THE PRODUCTION OF PRESSED BOARD FIELD OF THE INVENTION The present invention relates to a system for the production of pressed board and, more particularly, to a plant for the production of particle board, fiberboard and the like and to arrangements for controlling the means for displacing such board and the mats forming same through and between the operating devices of the plant.

BACKGROUND OF THE INVENTION In a production of pressed board, i.e., self-supporting structures formed by pressing a mass or mat of wood or other particles of fibers with added thermally activatable binder or an intrinsic binder as may be present in such particles or fibers, the mat is formed upon a conveyor directly or upon a tray adapted to transport the mat, may be advanced by one or more conveyor belts, and is hot-pressed generally after stacking, in a multiplaten press. Depending upon the proportion of binder and the nature of the particles and binder, and upon the parameters of the pressing operation, the resulting board may be relatively hard and dense for structural applications or may be relatively porous for insulating purposes. Such board, whether made from particles or fiber and whether of a hard or porous character can be termed generically pressed board.

In the production of such board it is increasingly common to deposit the mat directly upon a conveyor belt, to transfer mats from one conveyor belt to the next along the transport path of the mat and to provide prepress stages wherein, for example, the mat is passed between two stretches of belts moving in the transport direction and converging toward one another to generally squeeze the mat between them. Each conveyor may be provided with a transfer edge displaceable together with the trailing edge of a successive transport band to effect a smooth transfer of the mat with a minimum of distortion.

The mat-forming band may be provided with means for subdividing the continuous layer of particles of tibers and binder which is dispensed thereon by a layerforming device to form the individual mats and, beyond the press belts, conveyor systems may be provided for stacking the prepressed mats, feeding a number of such mats from respective tiers of a rack into respective openings of a multiplaten press, etc.

In order to provide the desired synchronization of some or all of the belts, it has been the practice heretofore to provide a so-called king shaft along the trans port path and to couple each of the transport and press belts with the king shaft by electrical or mechanical devices. This has the advantage that distortion of the mat and interruption of the feed thereof was precluded. As a consequence, the mat was not subjected to tensile stress tending to tear it, was not pushed from behind excessively to cause bunching, and otherwise remains free from distortion during advance along the transport path. However, problems were encountered when the system was desired to operate at high speeds or during acceleration of the processing line. Not unsurprisingly, these problems were found to arise from the fact that, on the one hand, the mats were required to pass through a pair of conveyors for continuous pressing and, on the other hand, were transported before, after and during traversal of this press on a transport conveyor.

OBJECTS OF THE INVENTION It is the principal object of the present invention to provide a system for the production of chipboard, fiberboard and the like which includes a transportconveyor system and a press conveyor (continuous operation) system so that the mats may be displaced through both systems without tearing. excessive compaction in the transport direction and without cracking or like distortion.

It is another object of the invention to provide an improved method of operating a system of this type.

SUMMARY OF THE INVENTION These objects and others to be described subsequently, are attained, in accordance with the present invention, by providing an installation for the production of press board, especially particle board, fiber board and the like, which comprises a transport conveyor system having one or more conveyor-drive drums and one or more conveyor bands driven thereby for the displacement of the press board or the mats adapted to be pressed in the formation of the boards along a transport path, and at least one continuously operating press for the compaction of particle or fiber mats and provided with a press conveyor and advancing the mat through the press (whereby the mat is engaged between upper and lower press-belt stretches), the invention residing in the provision of an independent drive mechanism for the transport conveyor system and for the press-conveyor system (each drive mechanism including a respective motor and a transmission operatively connecting the system motor to the drum of the respective conveyors), and means for intermittent synchronously connection of the two drive mechanisms. When the two drive mechanisms are said to be synchronously connected for synchronous operation, it is to be understood that the drive drums of the respective conveyors are so connected that a predetermined angular displacement of one corresponds to a predetermined angular of the other.

The invention resides in the provision of, on the one hand, independently operable drive motors and transmissions for each system (i.e., the press-conveyor system and the transport-conveyor system) and, on the other hand, means for synchronizing the two-conveyor driving drums at least at selective time intervals. Of course, the synchronization of the two systems can be accomplished in various ways.

In accordance with a feature ofthe invention, the two driving mechanisms are mechanically and synchronously connected for increasing the speed of the two conveyor systems to the operating speed of the installation whereby, upon attaining the operating speed, the mechanism synchronous coupling is interrupted and the press conveyor produces an output signal representing the torque applied to its drum and is used for controlling a drive motor.

More specifically, the invention relates to an apparatus for the production of pressed board which comprises a belt-type press having pressed belts with stretches moving in the transport direction and compacting a mat or layer of particulate or fibrous material between them at least one transport belt (hereinafter described as press-transport conveyor) extending through the press for displacing the layer or mats therethrough, and one or more ancillary transport conveyor belts disposed along the transport path for conveying the mats in a subdivided and prepressed state. The transport conveyors are here provided with one drive system including at least one motor and a transmission connected between the motor and the driving rollers of the transport conveyors (press-transport and auxiliary transport band) and a second drive means including a motor and transmission. connected to the press belt. Means is provided for mechanical coupling of the drive rolls or drums of the press belts and the transport belts (auxiliary and press transport conveyors) so they can be synchronously connected together for acceleration up to the operating speed. After reaching operating speed, the press-transport belt is decoupled and serves to generate a control signal for operating the press belts or the drive thereof so that synchronization between the press belts and the press-transport conveyor is as sured.

The invention is based upon the recognition that in the normal operating state, after acceleration of the mats or layers to the pre-operating speed, for example to advance the layer to the press, the distortion of the mats can be eliminated by ensuring that at least the transport belt (press transport belt) leading the mats or layers to or withdrawing them from the press are operated at full synchronization with the press belts.

One embodiment of the invention is characterized by the fact that the press-belt drive as well as the tran' sport-belt drive are mechanically synchronously cou pled to bring the apparatus up to operating speed. After operating speed has been reached the drive torque of the press-transport belt is detected and converted into a control signal which is used to operate the press'belt drive in synchronism.

The invention is based on the recognition that under normal operating conditions, after the system has been brought to operating speed and the entry of the compressible mass between the two press belts, breakdown and distortion of the layer can be prevented (in spite of the fact that press operates with varying conditions because of changes in the character of the layer) by precluding any overriding effect of the transport belt traversing the press and, further, when the press bands are driven from, or in synchronism with, the drive for this transport belt.

Using the torque feedback from the transport belt traversing the press to affect, for example, the field of the electric drive motor of the press belts, we ensure that the synchronism between the press belts and the transport belt traversing the press is maintained in spite of the variations in press effect introduced by th compressible layers and inhomogeneities thereof.

Suitable speed controls for this purpose are described in SERVOMECHANISM PRACTICE, McGraw-Hill Book Co.. New York, 1960.

It has been found to be especially advantageous to constitute the press-transport belt drive as a constantspeed controlled electric motor serving as a master motor whose speed is introduced as an input to the control device for the drive motor of the press belts to ensure synchronismf For the drive of the individual transport belts and auxiliary devices (such as the saw carriage advanceable in the transport direction during severance of a mat from the layer deposited upon the layer-forming surface and any lip or edge of a belt displaceable in this direction to effect deposition of a mat on a subsequent conveyor) individual slave or follower motors, coupled to the master motor, may be used. The master and follower motors may be electrically coupled synchronous.

The master motor may be provided with a transmission (step-down gearing) connected to the drive drum or roller of the transport band traversing the press while a torque sensor is provided on the shaft between this roller and the transmission to generate the control signal fed back to the press-belt motor. thereby constituting of this shaft a torque-measuring shaft. The presstransport conveyor can be constituted as a single endless belt but preferably is formed as two belts, an inner or support belt spanning the press zone and an outer belt which extends through the press from the layerforming device to a transfer edge at which the mats are transferred to a downstream accelerating belt designed to increase the spacing between the mats.

in the latter case, the drum of the torque-measuring shaft engages the outer or layer-carrying belt, while the support or inner belt has a drum or roller mechanically coupled via a suitable transmission to the shaft of the press-belt motor at least during acceleration of the sys tem to the operating speed. Thereafter, the support belt will be decoupled from the press-belt motor so that the support belt is entrained frictionally by the press belts as the layer is compressed between them while the outer band (Layer-carrying belt traversing the press) is driven from the master motor of the transportconveyor system.

As noted previously the press-traversing transport belt and, if desired, other transport belts, are provided with mat-transfer noses or edges which are advanced at the rate of advance of the mats and are retracted together with the trailing edge of a downstream conveyor so that the mats can be transferred from one conveyor to the other at an accelerated rate without exposing the mat to different conveyor-surface speeds as described in the prior patents listed below. To this end, the transfer edge and the respective trailing edge are provided upon a carriage reciprocable parallel to the direction of advance of the mats. The carriage is driven by a suitable transmission not only in accordance with the speed of the transport conveyors but also in dependence upon the phase angle of the corresponding motor, thereby precisely relating the position of the transfer edge with the advance of the mats. The reciprocable carriage is provided with a drive having a synchrofollower motor coupled to the master motor by a phaseangle control circuit in accordance with synchromotor principles.

The press-belt drive can include positive transmission means (e.g., meshing gears or a chain-and-sprocket arrangement) for connecting the upper and lower press belts for joint displacement to a common shaft. To reduce wear the upper and lower press belts can be connected to the respective output shafts of a differential whose input shaft is connected to the press-belt drive (motor and transmission), the differential having a lock to ensure nonslip connection of the upper and lower belts in the empty state of the press. The differential lock may be released automatically when a mat or the compressible layer enters the space between and is compressed by the belts.

According to another feature of the invention, the press belts on the one hand and the transport belts on the other hand are provided with independent drives, namely the press-belt drive and the transport-belt drive. The press-belt drive is provided with a torquecontrol system including means for establishing a setpoint valve, a comparator for the set-point valve and a control signal representing the actual press condition. a transducer or the like for generating the control signal and means responsive to the error-signal output of the comparator. The transport-belt drive is provided with a speed-control circuit having a set-point signal input device, a comparator for the set-point signal and the controlled-speed signal, a generator (tachometer) for producing the controlled-speed signal and means responsive to the error signal output of the comparator.

In this system the torque requirements of the continuously operable press belts are separated from the torque-requirements of the transport belt traversing the press. The press-traversing transport belt thus controls the displacement during the empty condition of the press and is under tension when the mat enters the press.

Preferably the torque-control circuit of the press-belt drive is set to maintain a constant torque at a level determined in accordance with the material compressed, e.g., by hand-setting of the set-point signal. Since the variations in the layer are generally small with modern mixing and dispensing devices for the layer-forming material, the hand-setting of the torque and speed controls will normally suffice.

Where an automatic compensation is required the set-point signal of the torque-control circuit can be responsive to the output of the comparator of the speedcontrol circuit to reset the former upon development of an error signal in the latter.

Here as well the press-traversing transport belt is entrained by the press drive under the press pressure and the press-belt drive responds to the constant speed of the transport-belt drive. The torque-control circuit may be automatically rendered ineffective during synchronous drive of the press belts and transport belt during the initial advance of the mat into the press.

DESCRIPTION OF THE DRAWING The above and other objects, features and advantages of the present invention will become more readily apparent from the following description, reference being made to the accompanying drawing in which:

FIG. 1 is a diagrammatic vertical section through a transport path for the production of pressed board according to the present invention, showing in flowdiagram and schematic form, the control elements for the several devices;

FIG. 2 is a view of a modification of the control system of FIG. 1;

FIG. 3 is a cross-sectional view through a portion of the transport path of another system;

FIG. 4 is a vertical elevational view, in diagrammatic form, showing a press installation according to a modification of the present invention; and

FIG. 5 is a control diagram of a system for use with the installation of FIG. 4.

SPECIFIC DESCRIPTION In FIGS. 1 and 2 we have shown the transport path of a line for the production of press board in a pressedboard plant. Upstream of the portion of the first band illustrated in FIG. 1 there is provided a layer-forming band upon which a layer of particles for fibers, with a thermally activated binder, is formed. Such a dispenser has been illustrated in U.S. Pat. NO. 3,565,725. This patent also shows an appropriate layer-forming band and means for subdividing the layer into individual mats, e.g., a saw which may be of the type shown in U.S. Pat. Nos. 3,428,505, 3,05 l ,2l9 or 3,096,227 (and can be one of the auxiliary devices mentioned previously). The individual mats are fed through a continuous prepressing stage and thereafter may be displaced on to a rack which is vertically shiftable as described in U.S. Pat. No. 3,525,725 and may consist of conveyor belts (conveyor pallets or tablets) which are shiftable in the transport direction to deposit the precompressed mats on the platens of a multi-platen press. Conveyor systems for the intermediate transport of the mats have been described in U.S. Pat. Nos. 3,077,271, 3,224,758, 3,288,057 and 3,379,322 which also describe the means for reciprocating the leading edge of one conveyor and the trailing side of the next to effect transfer of mats from one to the otherv The multi-platen press is preferably of the type described in U.S. Pat. Nos. 3,050,777 and 3,209,405 and may have heating means as described in U.S. Pat. No. 3,517,610. Details of the loading and discharge racks may be found in U.S. Pat. No. 3,206,800 or 3,050,200.

The layer-forming portion of the conveyor and the dispensing device, although upstream of the portion shown in FIG. 1, have not been illustrated here, nor has the multi-platen press been shown at th downstream end of the system. In the transport path illustrated, the extreme right hand side represents the vertically displaceable rack 3 of conveyor belts 3a which are made up of conveyors as described in U.S. Pat. No. 3,517,6l0, and deliver their mats to the respective platens of the multi-platen press. The transport path comprises a press-traversing transport conveyor 1 on which the layer is formed continuously as is shown at 2 from a mixture of wood chips, wood or other fibers, and a thermally activatable binder, and which is fed to the right as represented by the arrow 2a.

The layer 2 is prepressed, subdivided into mats, and eventually deposited upon the conveyor belts 3a of the rack 3 for introduction into the multi-platen press. After the pressing stroke, the rigid board is removed, and tempered in a kiln or otherwise treated as required.

Between the conveyor 1 and the rack 3, there are provided transport conveyors 4, 5, 6, all of the trans port conveyors 4-6 and the conveyor 1 which carries the mats through the press (press conveyor) are provided with drive drums 7,, 7,, 7 7 and 7 respectively.

The continuously operating press 8 is here shown to be a prepress which compacts the layer prior to its separation into individual mats but can be a prepress disposed between the mat separating means and the stacking device, or even a final pressing stage downstream of a prepress station at which the mat is consolidated to the desired density under heat and pressure.

The press-traversing transport conveyor 1 extends continuously through the press 8 which itself is constituted by upper and lower press belts 9 having drums 9a, 9b journaled for rotation in a support (not shown) with at least the drums 9b being driven as will be apparent hereinafter. The codirectionally moving stretches of the belts 9 define a convergent gap between them in the direction of arrow 20. The drums 9b are connected to the outputs of a differential whose input is the drive means (first drive means 11) of the press.

The press belts 9 are thus driven by a transmission 27a controlled by a regulator 28a adapted to vary the transmission ratio or output speed or torque of the shaft 9c connecting the transmission 27a to the rolls 9b. The input to the drive 270, 28a is a motor 15 which is connected to the input shaft 30 by a magnetic clutch 180, the output side of which is provided with an electromagnetic brake 150.

In the drawing heavy lines represent mechanical drive linkages while light lines represent the various control networks.

The transport conveyor 1 has a layer-forming and mat-forming belt, the transport conveyor 4 is a belt designed to accelerate the mats so that the spacing between them is increased and they may be advanced through the system at a rate higher than the feed of the layer-forming conveyor 1, a storage belt 5 is provided ahead of conveyor 4 for temporarily retaining the mat, and a conveyor pallet 6 (U.S. Pat. No. 3,5 l7,610) for depositing the mat upon the rack 3. The separating saw 10 which subdivides the layer into mats 2 is shiftable along the conveyor 1 as it moves transversely thereto and is provided for this purpose, with a transmission 27b, a brake 27b and a clutch 18b connecting the transmission 27b with a slave motor 21.

From FIG. 1 it should be apparent that the press belts 9 are provided with a drive 11 which is independent from the drive 12 for the transport conveyors l, 4, 5, 6. The drive 11 and the drive 12, however, are synchro' nously connectable by the mechanical linkage represented at 13 by engagement of the clutches 18c, 18d, 18a and 18f, for example.

After the desired operating speed of the apparatus is obtained, the press-transport conveyor 1 is decoupled and is operated by its motor 15 under the control of a device 14 to maintain synchronization. A detector (torque-measuring transducer) 16 is provided for the torque at the drum 7, and means 17 is provided for communicating the detected signal to the controller 14.

The mechanical coupling between the two drives 11 and 12 may use electromagnetic clutches 18 as shown in FIG. 2 and may be triggered by corresponding control pulses in accordance with the position of the lead ing edge of the compressible layer along the transport path.

Preferably, the system comprises a constant-speed controlled drive motor 19 for the transport drive 12 and constituting a master motor 19 which is connected by the magnetic clutch 18fto a shaft 19a ofa transmission 22. The output shaft 23 of this transmission is applied to the drive drum 7, of the conveyor 1 which comprises an outer band lb extending over a rigid carriage 25 and around a transfer nose or lip 24 and a plurality of guide rolls 24a and 24b before passing around the drum 7,. The shaft 23 also constitutes the torquemeasuring shaft which cooperates with the torque sensor l6 mentioned previously.

The press-transport conveyor 1 also comprises an inner belt 1a (support belt) which terminates short of the edge 24 about the drum 7, and is driven apart from the outer band 117. A shaft 110 is here coupled to the drum 7 and is, in turn, operated by a transmission 27c having a controller 280 connected therewith. The electromagnetic clutch 18d connects shaft 30 to the input of the controller 286. Conveyor belt la constitutes the supporting conveyor while conveyor belt 1b transport belt) forms a depositing surface for the layerforming mass. The supporting conveyor la is, however, not connected to the transport conveyor drive 12 but rather is mechanically connected via the system Ila, 27c, 28c, 1811 with the drive for the press belts 9 so that as the system is accelerated to operating speed and the press 8 remains open, the belt la is not positively entrained. Only when the layer reaches the press, are the belts lb and la frictionally urged together so that the belt la is entrained with the belt lb and the compressed layer through the press. The belt I1) is connectable to the motor 19.

The transfer edge 24 provided at the end of the belt lb and at the junction thereof with the accelerating belt 4, has a plate 25, as noted, which constitutes a carriage shiftable in the direction 20 of feed of the mats. The drive for this carriage is represented at 26 and includes a transmission 26a and a controller 2612 connected by a shaft 26c and a clutch 18c with the shaft previously described. Another clutch 18g connects a follower motor 21 to the input shaft 260. The follower motor 21 of drive 26 is controlled by a regulator 29a of the master motor 19 via a circuit 29. The phase angle control of motor 21 for the carriage drive 26 by motor 19 is thereby assured.

Phase angle control of the slave motor 21 for the carriage drive 26 may be effected in accordance with conventional synchro motor principles as described, for example, at page 74 through 98 of SERVOMECHANISM PRACTICE, McGraw-Hill Book Company, New York, Second Edition, I960. For the purposes of the present invention, the master motor 19 may be the controlling element of a synchro system as here described while the follower, slave or controlled motors 21 are electri cally connected therewith in accordance with the basic synchro transmission circuitry described in the latter work. In addition to being a drive motor, therefore, member 19 may be (or is coupled with) a synchro transmitter while the motors 21 may be synchro receivers.

The circuit of FIG. 2 thus provides transmissions 27 for connecting the respective synchro receivers 21 to the drive rolls of the successive transport belts 4, 5, 6 of the transport conveyor system and clutches 18 for mechanically connecting the drives for these conveyors together. Since the drive for roller 7, includes a transmission connected to the main drive 13, 19a and a secondary drive in the form of a follower synchro motor 21, the transport conveyors 1, 4, 5, 6 may be connected together and provided with a common drive 12.

The upper and lower press belts 9 have their rollers 9b connected by meshing gears, chain-and-sprocket arrangements or the like to the output shafts of a differential 31 whose input is tied to the shaft 30 of the first drive 11. Speed-changing gear sets or transmissions 27 may be provided between each output shaft and the respective roller 9b (FIG. 2) whose shafts are represented at 32 and 33. The differential may be of the type described at page 1 1-12 of MARKS MECHANICAL ENGINEERS HANDBOOK, McGraw-Hill Book Company, New York, 1958.

The operation of the system of FIGS. 1 through 3 is such that, until the leading edge of the layer 2 of compressible material reaches the press belts 9, the lock for the differential 31 is engaged and the two shafts 32 and 33 are coupled for non-slip rotation. The clutches l8c and 18 are engaged to mechanically connect the first and second drives 11 and 15 for direct-coupled synchro displacement under the control, for example, of motor 19. All of the belts are driven at high speed until the leading edge of the layer 2 passes between the press belts 9.

At this point, the press belts 9 are loaded and the lock of differential 31 is automatically released to permit differential operation of the upper and lower press belts at a rate which precludes wear of the press belt and dis tortion of the layer. The clutch 180 is decoupled and clutches 18a and 18f are engaged. Clutch 18d, which has been engaged during acceleration of the belts to provide a positive drive to the support belt 1a, is also decoupled and motors I and 19 govern the advance of belts 9 and lb.

As the layer 1 is drawn between the two press belts 9, the compression force presses the upper belt lb against lower belt la and, in turn, against the lower belt (FIG. 3) so that the inner belt la is dragged along synchronously with the press belts.

The sensor 16 detects the torque at the torquemeasuring shaft 23 and applies a control signal to the servoregulator 14 which controls the motor 15. The output input to the servocontroller is a constant speed signal for a tachometer 14a applied via the electrical connection 20 to the circuit 14 so that the motor responds on the one hand to a torque signal and on the other hand to a speed signal derived from the synchro meter 19. The several conveyors 4, 5, 6 are also driven in response to the synchro transmitter 19 via the synchro receivers 21 associated therewith.

As the precompressed layer 2 emerges from the press at a rate which is a function of the nature of the compressed material and the torque conditions mentioned previously, the saw 10 severs a mat from the layer. During this operation, see US. Pat. Nos. 3,051,219, 3,096,227 and 3,428,505, the saw is advanced in the direction of arrow 2a by its synchro receiver 21 and an appropriate kinetic linkage connected to the transmission 27b, it is advanced to the right by the carriage which thereafter reacts while the mat continues its advance without relative movement of the supporting sur face of belt lb and the mat. The mat is thereby accelerated to increase the space between it and the subsequent mat and is thereafter transferred to the storage conveyor 5 for eventual passage onto a stacking conveyor 6. The latter is of the type described in the aforementioned patent and passes over the associated surface of rack 3, which is elevatable to position its successive tiers in line with the conveyor 6, so that each mat is deposited on a tier as the conveyor 6 is retracted. The mats on the rack 3 are thereupon simultaneously introduced into the multi-platen press.

The system shown in FIGS. 4 and 5 differs from that illustrated in FIGS. 1 and 2 in some respects and in some respects is similar. In FIG. 4, we have shown the press 8 with upper and lower press belts 9, the layerforming press-traversing conveyor 1, the subsequent conveyor 4, a rack 3, all as described in connection with FIG. 1.

Upstream of the press 8, however, there is shown a dispensing station 38 for depositing the layer upon the upper surface of belt 1b which here constitutes a matforming conveoyor. Downstream of the rack 3 is a mu]- ti-platen press 34. The conveyor system also includes a belt 35 for feeding the pressed mats to the rack 3, the latter having conveyor belts 37 for transferring the mats to the respective tiers of the multi-platen press 34.

The conveyors are formed with transfer edges 24, 36 on respective carriages for facilitating transfer between the conveyors. The transfer-edge carriages, of course. operate intermittently while the belts are displaced continuously, the dispenser 38 operates continuously and rack 3 and platen press 34 operate intermittently. The intermittently operable saw 10 may also be provided as described in connection with FIGS. l and 2.

The conveyor belts la, lb, 4 and 35 are provided with drive drums on rolls 7a, 7b, 7c and 7d, respectively, connected to a common drive for synchronous operation. The driving system has been illustrated in greater detail in FIG. 5.

In the system of FIG. 5, the first drive 111 has a transmission 1270 connected by a shaft 109 to the press belt 9, preferably via a differential as described in connection with FIG. 2. The transmission 1270 is operated by a servomotor 115.

The transport-conveyor drive 112 comprises a synchronous receiver motor 121a, a respective transmis sion 127 and its associated control system 128 tied via shaft 102 to the roller 7b of the press-traversing conveyor lb.

A second synchronous receiver l2lb has its transmission l27b connected via an appropriate linkage to the saw 10 for reciprocating same in the direction of advance of the compressible material.

A further follower motor 1210 is connected by a transmission 1270 and a similar linkage 124, converting rotary movement into linear reciprocation, for the carriage of the transfer edge 24.

A follower motor 121d having a speed-reduction transmission 127d and a control device 128d is connected to the drive roll 7c of conveyor 4 via the shaft 104 while a further follower motor l21e has a transmis sion 1272 and control device 128e likewise connected to the shaft 104. The motors l2ldand l2le are set to operate at different speeds in response to the input from motor 19 as selected by a switch 40 so that the high speed motor may be used for accelerating the system to operating speed while the low speed system is employed for normal operation.

Another follower motor l2lfis connected by a transmission l27f at a linkage to the conveyor 35 while a similar follower motor 121g, the transmission 127g and control device 1283 is provided for the shaft 137 operating the conveyor pallets 37. Of course, in place of the drive drums, other mechanisms may be used, to displace the belts.

In the system of FIG. 5, the press-belt drive 11 is provided with a torque-control circuit 41 including a setpoint input device 42, a comparator 43 for the set-point signal of the control signal representing the actual torque, and a transducer 44 for generating the actual torque signal. Transducers set-point generating devices and comparators of this type are fully described in SERVOMECHANISM PRACTICE cited earlier. The output from comparator 43 is applied via a servoamplifier to the servomotor 115.

The second drive 112 is provided with a speedcontrolling servomechanism 45 including the set-point generator 46, the comparator 47 and a transducer 48,

e.g., a tachometer, for generating the actual or control point speed-responsive signal.

Using the system of FIG. 5, the torque-control circuit 41 may be set to maintain a constant torque system press-belt drive which may be manually adjusted (by the set-point signal) for various compressible layers. In this case, the speed controlling circuit 45 is set to maintain a constant speed of the second drive 112.

Preferably, as represented by the dot-dash line, the comparator 49 of a phase angle control circuit 50 is connected with the set-point input 42 of the torque control circuit 41 whereby the set-point torque value is varied in accordance with deviations of the speed. The synchro motors 121a 121g respond to the synchro transmitter 51 connected to the direct-current motor 119 which is controllable via an adjustable rectifier 52 tied to the alternating current supply 53. With the aid of control circuit 45, the synchro generator 51 is held at a constant speed and frequency so that all synchro motors l2la l2lg are driven at the same constant speed. The synchro drive for the belts 1, 4, 35 and 37 can be provided with speed-controlled individual DC motors, in which case the drive motor 115 of the press belt is set by circuit 54 for a constant torque.

We claim:

1. In an apparatus for the production of pressed board comprising a press having upper and lower press belts and transport conveyors for advancing a layer of compressible material into, through and beyond said press, said conveyors including a press-traversing belt, said press-traversing belt at least intermittently being synchronized with said press belts, the improvement which comprises a first drive operatively connected to said press belts for driving same, a second drive operatively connected to said conveyors and independent of said first drive, and further comprising means for mechanically synchronously coupling said drives for accelerating said belts to a normal operating speed for compression of said layer between said press belts, and for decoupling said drives upon attainment of said speed, said first drive including a motor, a device responsive to the torque at said press-traversing belt for producing a control signal upon decoupling of said drives by the lastmentioned means, and means respon sive to said signal for controlling said motor to maintain synchronism of said press-traversing and press belts.

2. In an apparatus for the production of pressed board comprising a press having upper and lower press bolts, and transport conveyors for advancing a layer of compressible material into, through and beyond said press, said conveyors including a press-traversing belt, said presstraversing belt at least intermittently being synchronized with said press belts, the improvement which comprises a first drive operatively connected to said press belts for driving same, a second drive operatively connected to said conveyors and independent of said first drive, and wherein said second drive includes a constant speedcontrolled master motor, and said first drive comprises another motor, said improvement further comprising means for controlling said other motor in accordance with the speed of said master motor to maintain synchronism of said press-traversing and press belts.

3. In an apparatus for the production of pressed board comprising a press having upper and lower press bolts, and transport conveyors for advancing a layer of compressible material into, through and beyond said press, said conveyors including a press-traversing belt, said press-traversing belt at least intermittently being synchronized with said press belts, the improvement which comprises a first drive operatively connected to said press belts for driving same, a second drive operatively connected to said conveyors and independent of said first drive, and wherein said second drive includes a master motor operatively connectable to said presstraversing belt and respective slave motors coupled to said master motor and operatively connected to others of said conveyors.

4. The improvement defined in claim 3, further comprising an auxiliary device shiftable along the path of the layer, and a slave motor coupled to said master motor for displacing said auxiliary device.

5. The improvement defined in claim 3, further comprising a roll engaging said press-traversing belt, a shaft connected to said roll, a transmission connecting said shaft to said master motor, and means responsive to the torque at said shaft for controlling said first drive.

6. The improvement defined in claim 3 wherein one of said conveyors includes a transfer edge provided with a carriage reciprocable in the direction of advance of the layer for transferring said layer from said one of said conveyors to a successive conveyor, said improvement further comprising a phase-angle responsive slave motor coupled to said master motor and operatively connected to said carriage for displacing same.

7. In an apparatus for the production of pressed board comprising a press having upper and lower press bolts, and transport conveyors for advancing a layer of compressible material into, through and beyond said press, said conveyors including a press-traversing belt, said press-traversing belt at least intermittently being synchronized with said press belts, the improvement which comprises a first drive operatively connected to said press belts for driving same, a second drive operatively connected to said conveyors and independent of said first drive, and further comprising a support belt within said press-traversing belt and spanning the length of said press, and means for selectively connecting said support belt to said first drive during acceleration of said belts to advance said layer into said press and for disconnecting said support belt from said first driven upon entry of said layer into said press.

8. In an apparatus for the production of pressed board comprising a press having uper and lower press bolts, and transport conveyors for advancing a layer of compressible material into, through and beyond said press, said conveyors including a press-traversing belt, said press-traversing belt at least intermittently being synchronized with said press belts, the improvement which comprises a first drive operatively connected to said press belts for driving same, a second drive operatively connected to said conveyors and independent of said first drive, and wherein said first drive includes a motor, a torque-responsive element responsive to the torque at said press belts for generating a controlled torque signal, another element for generating a torque set point signal, and a comparator connected to said elements for producing a torque error signal for controlling said motor in response to said torque error signal; and said second drive includes another motor, a speed-responsive element responsive to the speed of said press-traversing belt for generating a controlled speed signal, another element for generating a speed set-point signal, and a comparator connected to the lat- 11. The improvement defined in claim 8 wherein the comparator of said second drive is connected to said other element of said first drive for varying the torque set-point signal.

12. The improvement defined in claim 8, further comprising a speed-controlling circuit for said motor of said first drive effective during displacement of said belts during advance of said layer to said press. 

1. In an apparatus for the production of pressed board comprising a press having upper and lower press belts and transport conveyors for advancing a layer of compressible material into, through and beyond said press, said conveyors including a press-traversing belt, said press-traversing belt at least intermittently being synchronized with said press belts, the improvement which comprises a first drive operatively connected to said press belts for driving same, a second drive operatively connected to said conveyors and independent of said first drive, and further comprising means for mechanically synchronously coupling said drives for accelerating said belts to a normal operating speed for compression of said layer between said press belts, and for decoupling said drives upon attainment of said speed, said first drive including a motor, a device responsive to the torque at said press-traversing belt for producing a control signal upon decoupling of said drives by the last-mentioned means, and means responsive to said signal for controlling said motor to maintain synchronism of said press-traversing and press belts.
 1. In an apparatus for the production of pressed board comprising a press having upper and lower press belts and transport conveyors for advancing a layer of compressible material into, through and beyond said press, said conveyors including a press-traversing belt, said press-traversing belt at least intermittently being synchronized with said press belts, the improvement which comprises a first drive operatively connected to said press belts for driving same, a second drive operatively connected to said conveyors and independent of said first drive, and further comprising means for mechanically synchronously coupling said drives for accelerating said belts to a normal operating speed for compression of said layer between said press belts, and for decoupling said drives upon attainment of said speed, said first drive including a motor, a device responsive to the torque at said press-traversing belt for producing a control signal upon decoupling of said drives by the last-mentioned means, and means responsive to said signal for controlling said motor to maintain synchronism of said presstraversing and press belts.
 2. In an apparatus for the production of pressed board comprising a press having upper and lower press bolts, and transport conveyors for advancing a layer of compressible material into, through and beyond said press, said conveyors including a press-traversing belt, said press-traversing belt at least intermittently being synchronized with said press belts, the improvement which comprises a first drive operatively connected to said press belts for driving same, a second drive operatively connected to said conveyors and independent of said first drive, and wherein said second drive includes a constant speed-controlled master motor, and said first drive comprises another motor, said improvement further comprising means for controlling said other motor in accordance with the speed of said master motor to maintain synchronism of said press-traversing and press belts.
 3. In an apparatus for the production of pressed board comprising a press having upper and lower press bolts, and transport conveyors for advancing a layer of compressible material into, through and beyond said press, said conveyors including a press-traversing belt, said press-traversing belt at least intermittently being synchronized with said press belts, the improvement which comprises a first drive operatively connected to said press belts for driving same, a second drive operatively connected to said conveyors and independent of said first drive, and wherein said second drive includes a master Motor operatively connectable to said press-traversing belt and respective slave motors coupled to said master motor and operatively connected to others of said conveyors.
 4. The improvement defined in claim 3, further comprising an auxiliary device shiftable along the path of the layer, and a slave motor coupled to said master motor for displacing said auxiliary device.
 5. The improvement defined in claim 3, further comprising a roll engaging said press-traversing belt, a shaft connected to said roll, a transmission connecting said shaft to said master motor, and means responsive to the torque at said shaft for controlling said first drive.
 6. The improvement defined in claim 3 wherein one of said conveyors includes a transfer edge provided with a carriage reciprocable in the direction of advance of the layer for transferring said layer from said one of said conveyors to a successive conveyor, said improvement further comprising a phase-angle responsive slave motor coupled to said master motor and operatively connected to said carriage for displacing same.
 7. In an apparatus for the production of pressed board comprising a press having upper and lower press bolts, and transport conveyors for advancing a layer of compressible material into, through and beyond said press, said conveyors including a press-traversing belt, said press-traversing belt at least intermittently being synchronized with said press belts, the improvement which comprises a first drive operatively connected to said press belts for driving same, a second drive operatively connected to said conveyors and independent of said first drive, and further comprising a support belt within said press-traversing belt and spanning the length of said press, and means for selectively connecting said support belt to said first drive during acceleration of said belts to advance said layer into said press and for disconnecting said support belt from said first driven upon entry of said layer into said press.
 8. In an apparatus for the production of pressed board comprising a press having uper and lower press bolts, and transport conveyors for advancing a layer of compressible material into, through and beyond said press, said conveyors including a press-traversing belt, said press-traversing belt at least intermittently being synchronized with said press belts, the improvement which comprises a first drive operatively connected to said press belts for driving same, a second drive operatively connected to said conveyors and independent of said first drive, and wherein said first drive includes a motor, a torque-responsive element responsive to the torque at said press belts for generating a controlled torque signal, another element for generating a torque set-point signal, and a comparator connected to said elements for producing a torque error signal for controlling said motor in response to said torque error signal; and said second drive includes another motor, a speed-responsive element responsive to the speed of said press-traversing belt for generating a controlled speed signal, another element for generating a speed set-point signal, and a comparator connected to the latter two elements for producing a speed error signal for controlling said other motor.
 9. The improvement defined in claim 8 wherein said elements, comparator and motor of said first drive are connected to maintain a constant torque at said press belts.
 10. The improvement defined in claim 8 wherein said elements, comparator and motor of said second drive are connected to maintain a constant speed of said second drive.
 11. The improvement defined in claim 8 wherein the comparator of said second drive is connected to said other element of said first drive for varying the torque set-point signal. 